Angioplasty is an established procedure for reducing the effect of atherosclerotic plaque on and intraluminal narrowing of the arterial walls within the vascular system of the patient. The effect is reduced by use of a catheter that is inserted into the site of the diseased-occluded vessel. A balloon portion of the catheter is then inflated to a predetermined pressure range and size, to radially compress the plaque occlusion, thereby increasing the internal diameter of the previously restricted artery. The balloon is then collapsed and the catheter is removed.
After the angioplasty procedure has been performed, as many as one-third to one-half of the patients soon develop restenosis. Restenosis can occur after angioplasty or other recannulation procedures, with or without stenting, wherein the migration and proliferation of benign cells cause a restenotic lesion to form, resulting in the further blockage of the intravascular structure.
Radiation is administered to patients for a variety of reasons, such as to treat restenosis, malignant or benign tumors, or the like. Examples of such treatments are disclosed in U.S. Pat. Nos. 5,059,166; 5,213,561; and 5,302,168.
It would be preferred to be able to provide a radiation delivery system which would:
a) deliver a predetermined totally-cumulative and homogeneous dose of radiation to the lesion site, at a predetermined penetration depth, while minimizing the exposure of surrounding healthy tissue to the radiation; PA1 b) enable the treating physician or other health-care personnel to be bedside to the patient during the administration of the radiation therapy without exposing the physician or health care personnel to any unreasonable risk; PA1 c) use radiation material that is readily and inexpensively available from a commercial provider; PA1 d) use minimal special equipment storage, or delivery devices, except for routine facilities available in most nuclear medicine or radiation oncology departments; PA1 e) use a radiation carrier material that if applied as an unsealed free-gas form, the inert, noble gas properties essentially enable the molecules of the carrier material to rapidly dissipate throughout the body of the patient without any prolonged organ accumulation or chemical interaction, and rapid dilution of the carrier material is quickly re-released from the bloodstream through the lungs; PA1 f) minimize long term occlusion of normal blood flow during therapy, thereby providing more flexibility as to administration time and dosage; PA1 g) use a radiation carrier material that is stable and which can be pressurized, stored, and made to high millicurie activity per cubic centimeter with reasonable cost and availability; PA1 h) use beta particles having excellent initial dose rate delivery and energy transfer when directly adjacent to the targeted tissue within the first one millimeter, and not penetrate much beyond this depth; PA1 i) use gamma photon energies having depth doses that provide complementary dose deposition with the beta particles for the first one millimeter, and primary additive dose delivery for an additional two to three millimeters of the targeted tissue; PA1 j) use these beneficial physical and biological radiation properties for treating restenosis, and malignancies (for example--in the brain, lung, esophagus, trachea, cervix, biliary ductal system, colon or rectum, the gastrointestinal system, the gynecological system, or head and neck) and other internal ailments where an internal application of radiation directly applied to the tissue may be needed; and PA1 k) attenuate the transmission dose to blood circulating through the apparatus, and while creating increased by-product radiation, delivering useful radiation dose over hundreds of micrometers of target tissue.